1. Field of the Invention
The present invention relates to a weather strip to be installed along an opening of a vehicle body or a closing member such as a door and a trunk lid for closing the opening of the vehicle body.
2. Description of the Prior Art
The above described weather strip comprises a base portion 11 having a U-shaped cross section, a seal portion 12a projecting from an outer surface of the base portion 11 and if necessary, a sub-seal portion 12 as shown in FIG. 2(c).
The base portion 11 is made of solid rubber and is provided with retaining lips 13 in its inner surface for retaining a flange of the opening of the vehicle body or the like. In the U-shaped base portion is embedded a core member 14 made of a sheet metal for improving the shape-retentivity of the U-shaped base portion and increasing the retaining force for the flange. The seal members 12a and 12b are made of sponge rubber.
FIG. 3 illustrates one example of the core member 14 and FIGS. 1 and 2 illustrate the conventional producing process of a weather strip in which the core member 14 is embedded.
The core member 14 is provided with slots 141 in a strip-shaped sheet metal at regular intervals in the longitudinal direction thereof. And cut lines 142 are formed from both ends of every other slots 141 to both side edges of the sheet metal.
When bending stress is applied to the sheet metal in the direction perpendicular to the surface thereof, the bending stress is concentrated to the cut lines 142. This results in the sheet metal being broken in the cut lines 142 to be separated into a large number of core pieces.
At first the core member 14 made of a sheet metal is fed out of a reel 2 and is extruded with solid rubber and sponge rubber by means of an extruder 3 to obtain an extruded body.
FIG. 2(B) illustrates the section of the extruded body. The core member 14 is covered with solid rubber and retaining lips 13 project from the under surface of the solid rubber while the seal portions 12a and 12b made of sponge rubber project from the upper surface of the solid rubber.
Next, the extruded body is fed to a high frequency induction heating apparatus 4 and then fed to a high frequency dielectric heating apparatus 5.
In the high frequency induction heating apparatus 4, the core member 14 is heated up to 120.degree. to 150.degree. C. and in the high frequency dielectric heating apparatus 5, the rubber material is heated up to about 200.degree. to 220.degree. C.
The extruded body is kept at about 200.degree. C. while passing a hot air bath 6 to be cured. The cured body is received by a receiver 7 and is cooled in a cooling bath 8.
In the high frequency dielectric heating, the temperature of the rubber rises but that of the metallic core member does not rise. This results in the heat of the rubber in the vicinity of the unheated core member being taken away thereby and accordingly the rubber in the vicinity of the unheated core member being not cured.
In order to prevent the above phenomena, conventionally, the metallic core member 14 is previously heated in the high frequency induction heating process prior to the high frequency dielectric heating process.
The cooled extruded body is then fed to a core member separator 9. In the separator, bending stress is repeatedly applied to the extruded body by rollers in the direction perpendicular to the surface of the extruded body. This results in the core member 14 within the extruded body being broken in the cut lines 142 to be separated into a large number of core pieces.
And then the extruded body is fed to a bending machine 10. In this step, the solid rubber portion enclosing the core member 14 is bent to form the base portion 11 having a U shaped section as shown in FIG. 2(c). Thus, a weather strip is obtained. The obtained weather strip is cut to a predetermined length by means of a cutter 30.
A weather strip is required to be of light weight as well as to have a good sealing force. For achieving the above requirement, the sheet metal for the core metal has been made thinner. Generally, the thickness of the sheet metal is about 0.5 mm and recently the sheet metal as thin as about 0.4 mm has been also employed. However, it is very difficult to make the sheet metal thinner than 0.4 mm.
In addition, in the weather strip in which the core member is embedded, there often occurs that the rubber cover covering the core member is torn and accordingly, the core member is exposed to the outside of the weather strip.
The rubber cover is easily torn particularly in the vicinity of an edge of the core member.
The exposure of the core member makes the obtained weather strip poor looking and incurs a problem that the exposed core member becomes rusty and accordingly, corrosion expands throughout the core member.
As described above, a long process is needed to produce the weather strip enclosing the core member. Therefore, a simplified method has been required.
Particularly, in the core member separation process for breaking the metallic core member, bending stress must be repeatedly applied to the core member. Usually, fifteen stations are necessary. In addition, large load as large as 4 kg/cm.sup.2 is required to bend the core member into the U-shaped cross section.
Under the above circumstances, simplification of the production process, particularly the core member separation process and the core member bending process has been strongly desired.